A137612 Greater of a pair of closest (n-digit) distinct primes that add up to 10^n.

7, 53, 509, 5081, 50123, 500057, 5000087, 50000243, 500000069, 5000000063, 50000000189, 500000000231, 5000000001569, 50000000000381, 500000000000231, 5000000000001443, 50000000000001113, 500000000000000321, 5000000000000000339, 50000000000000001353, 500000000000000000363

Offset: 1

Author

Lekraj Beedassy, Jan 29 2008

Keywords

• nonn
• base

Links

• Robert Israel, Table of n, a(n) for n = 1..300

Crossrefs

Cf. A124049, A137611.

Programs

Maple

f:= proc(n) local t,p;
  p:= 5*10^(n-1);
  do
    p:= nextprime(p);
    if isprime(10^n - p) then return p fi
  od
end proc:
map(f, [$1..30]); # Robert Israel, Jan 13 2025

PARI

a(n) = local(t);n=10^n;t=nextprime(n/2+1);while(!isprime(n-t),t=nextprime(t+1));t \\ Charles R Greathouse IV, Sep 29 2008

Formula

a(n) = 5*10^(n-1) + A124049(n) for n > 1. - Robert Israel, Jan 12 2025

Extensions

a(7)-a(30) from Charles R Greathouse IV, Sep 29 2008

More terms from Michel Marcus, Jan 13 2025